PUNCHED TAPE

Punched Tape

Punched tape is a mechanical form of data storage, consisting of a long strip of paper or other material in which holes are punched to store data. Data is represented by the presence or absence of a hole at a particular location which is a binary representation that can store one bit. Tapes originally had five rows of holes for data (5 bits for one column) and later tapes had six, seven and eight rows. A row of narrower holes that were punched served to feed the tape, originally using a wheel with radial teeth called a sprocket wheel. Mechanical tape readers used in most of the early machines sensed the holes by means of blunt spring-loaded sensing pins. Later optical readers were developed. Now effectively obsolete, it was widely used during much of the twentieth century for teleprinter communication, for input to computers of the 1950s and 1960s, and later as a storage medium for minicomputers.

Konrad Zuse's machines Z1, Z2, Z3 and Z4 used punched film to store program code. For the tape feeding he used the perforations along both edges of the film that were already in place for the film transportation. Some other early electromechanical calculating machine used punched tape as well.